Distinguishing the Mélange-Forming Processes in Subduction-Accretion Complexes: Constraints from the Anisotropy of Magnetic Susceptibility (AMS)
| Autor: | Emanuele Scaramuzzo, Andrea Festa, Elena Zanella, Giulia Codegone, Claudio Robustelli Test |
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| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
010504 meteorology & atmospheric sciences
Subduction lcsh:QE1-996.5 Mesoscale meteorology 010502 geochemistry & geophysics 01 natural sciences Magnetic susceptibility magnetic fabric Sedimentary depositional environment lcsh:Geology Tectonics mélanges Ligurian accretionary complex Northern Apennines diagnostic criteria General Earth and Planetary Sciences Sedimentary rock AMS Anisotropy Petrology Accretion (geology) Geology 0105 earth and related environmental sciences |
| Zdroj: | Geosciences, Vol 9, Iss 9, p 381 (2019) Geosciences Volume 9 Issue 9 |
| ISSN: | 2076-3263 |
| Popis: | The strong morphological similitude of the block-in-matrix fabric of chaotic rock units (mé langes and broken formations) makes problematic the recognition of their primary forming-processes. We present results of the comparison between magnetic fabric and mesoscale structural investigations of non-metamorphic tectonic, sedimentary, and polygenetic mé langes in the exhumed Late Cretaceous to early Eocene Ligurian accretionary complex and overlying wedge-top basin succession in the Northern Apennines (northwest Italy). Our findings show that the magnetic fabric reveals diagnostic configurations of principal anisotropy of magnetic susceptibility (AMS) axes orientation that are well comparable with the mesoscale block-in-matrix fabric of mé langes formed by different processes. Broken formations and tectonic mé langes show prolate and neutral-to-oblate ellipsoids, respectively, with magnetic fabric elements being consistent with those of the mesoscale anisotropic &ldquo structurally ordered&rdquo block-in-matrix fabric. Sedimentary mé langes show an oblate ellipsoid with a clear sedimentary magnetic fabric related to downslope gravitational emplacement. Polygenetic mé langes show the occurrence of a cumulative depositional and tectonic magnetic fabric. The comparison of field and laboratory investigations validate the analysis of magnetic features as a diagnostic tool suitable to analytically distinguish the contribution of different mé lange forming-processes and their mutual superposition, and to better understand the geodynamic evolution of subduction-accretion complexes. |
| Databáze: | OpenAIRE |
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